EP1113633B1 - Dispositif et procédé d'estimation de canal dans un système de communication par radio - Google Patents

Dispositif et procédé d'estimation de canal dans un système de communication par radio Download PDF

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Publication number
EP1113633B1
EP1113633B1 EP00128658A EP00128658A EP1113633B1 EP 1113633 B1 EP1113633 B1 EP 1113633B1 EP 00128658 A EP00128658 A EP 00128658A EP 00128658 A EP00128658 A EP 00128658A EP 1113633 B1 EP1113633 B1 EP 1113633B1
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EP
European Patent Office
Prior art keywords
interpolator
symbols
signal
channel
inverter
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP00128658A
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German (de)
English (en)
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EP1113633A2 (fr
EP1113633A3 (fr
Inventor
Kyu-Hak Kim
Je-Woo Kim
Hyung-Suk Kim
Ki-Soo Kim
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Samsung Electronics Co Ltd
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Samsung Electronics Co Ltd
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Publication date
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Publication of EP1113633A3 publication Critical patent/EP1113633A3/fr
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Publication of EP1113633B1 publication Critical patent/EP1113633B1/fr
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/76—Pilot transmitters or receivers for control of transmission or for equalising
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0212—Channel estimation of impulse response
    • H04L25/0214—Channel estimation of impulse response of a single coefficient
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0224—Channel estimation using sounding signals
    • H04L25/0228—Channel estimation using sounding signals with direct estimation from sounding signals
    • H04L25/023—Channel estimation using sounding signals with direct estimation from sounding signals with extension to other symbols
    • H04L25/0232—Channel estimation using sounding signals with direct estimation from sounding signals with extension to other symbols by interpolation between sounding signals

Definitions

  • the present invention relates generally to data demodulation in a radio communication system, and in particular, to an apparatus and method for demodulating data against signal distortion caused by fading or other factors.
  • Radio communication technology mainly cellular communication technology has been rapidly developed and GMPCS (Global Mobile Personal Communication System) is being deployed for communication throughout the world.
  • GMPCS Global Mobile Personal Communication System
  • predetermined symbols e.g., pilot symbols
  • a transmitter inserts agreed symbols between data symbols prior to transmission and a receiver extracts those agreed symbols for use in channel estimation.
  • Conventional channel estimation relies on the use of an interpolator or extended symbol-aided estimation (ESAE).
  • FIG. 1 is a schematic block diagram of a conventional channel estimating apparatus in a radio communication system for data recovery.
  • FIG. 2 is the format of a frame used in the conventional radio communication system.
  • FIG. 3 is a detailed block diagram of the conventional channel estimating apparatus in the radio communication system.
  • FIG. 4 is a block diagram of another conventional channel estimating apparatus relying on ESAE in a radio communication system and
  • FIG. 5 conceptually illustrates channel estimation for data recovery relying on the ESAE.
  • FIG. 1 illustrates a channel estimating apparatus using pilot symbols for channel estimation in a PSAM (Pilot Symbol Assisted Modulation) system.
  • PSAM Packet Symbol Assisted Modulation
  • pilot symbols are periodically inserted by pilot symbol inserter 101 between data symbols and the entire signal is pulse-shaped by pulse shaper 102 prior to transmission.
  • Fading and AWGN are added to the transmission signal by multiplier 103 and adder 104, respectively.
  • a receiver separates an input signal into pilot symbols and data symbols by passing the input signal through a matched filter 105 and estimates the channel of data symbols using the pilot symbols.
  • an interpolator 108 is required and data is recovered using the interpolation result.
  • Delay 106 compensates for the signal delay through interpolator 108.
  • St(t) is the transmitter signal
  • Re[zO(t)exp(j2 ⁇ fct)] represents the real number part of zO(t)exp(j2 ⁇ fct)
  • fc is a carrier frequency
  • zO(t) is a transmission baseband signal with its band limited by a transmission filter.
  • preset pilot symbols are inserted into a transmission frame.
  • Sr(t) is the received signal
  • nc(t) is the AWGN component.
  • U t C t Z t + n t
  • Fading-caused distortion of an information symbol can be detected using an interpolator as applied to Eq. (8).
  • interpolation methods There are generally two interpolation methods: fixed interpolation and adaptive interpolation.
  • fixed interpolation a sync (Nyquist), Gaussian, linear, or a cubic interpolator is applied throughout a channel to estimate the distortion of the channel regardless of channel variation
  • adaptive interpolation for example, a Wiener interpolator using a Wiener filter accurately estimates a channel by adaptively compensating for channel variation utilizing parameters like Doppler frequency and symbol energy per power spectrum density (Es/No).
  • FIG. 3 is a conceptual view of the fading estimation and compensation using a sync interpolator.
  • a fading estimator 301 estimates fading of pilot symbols and an interpolator 302 interpolates data symbols based on the channel estimation of the pilot symbols.
  • the channel estimation result is reflected in an input signal delayed by a delay 304, to thereby compensate the input signal.
  • FIGs. 4 and 5 illustrate the other channel estimation scheme, ESAE.
  • a receiver separates an input signal into pilot symbols and data symbols by passing the input signal through a matched filter 401.
  • an interpolator 403 is required and data is recovered using the interpolation result.
  • First delay 402 compensates for the signal delay through interpolator 403.
  • Demodulator 405 demodulates the signal. As shown in FIG. 5, recovered data before a symbol "S" is used along with pilot symbols "P1", “P2", “P3", and "P4" to estimate the channel of the symbol "S".
  • the data estimation scheme using pilot symbol channel estimation and the ESAE scheme have shortcomings in that channel estimation is not reliable when a received signal has weak strength or experiences severe fading.
  • the channel estimating apparatus for a radio communication system in accordance with the preamble part of claim 1 is known from EP-A-0 715 440.
  • the object of the present invention to provide a channel estimating apparatus and method capable of channel estimation even in an environment where fading causes severe distortion.
  • a fading estimator estimates a channel using preset symbols of an input signal
  • a first interpolator interpolates the other symbols of the input signal based on the fading estimation
  • a first inverter inverts the output signal of the first interpolator
  • a first delay delays the input signal for a predetermined time
  • a first multiplier primarily compensates the output signal of the first delay by means of the output signal of the first inverter
  • a second interpolator interpolates each symbol of the input signal relating to primarily compensated symbols in a predetermined period before and after the symbol
  • a level controller controls the level of the output signal of the second interpolator
  • a second inverter inverts the output signal of the level controller
  • a second delay delays the primarily compensated signal for a predetermined time
  • a second multiplier secondarily compensates the output signal of the second delay by means of the output signal of the second in
  • FIG. 6 is a block diagram of a channel estimating apparatus according to an embodiment of the present invention
  • FIG. 7 is a conceptual view of channel estimation for data recovery according to the embodiment of the present invention.
  • a fading estimator 600 estimates fading using preset pilot symbols in an input signal.
  • a first interpolator 610 interpolates information symbols based on the fading estimation.
  • a Wiener interpolator may be used as the first interpolator 610.
  • a first inverter 620 obtains the reciprocal number of the output of the first interpolator 610 through inverting.
  • a first delay 630 delays an input signal for a predetermined time to provide action time to the fading estimator 600, the first interpolator 610, and the first inverter 620.
  • a multiplier 640 primarily compensates the delayed signal received from the first delay 630 using the channel estimation signal inverted by the first inverter 620.
  • the primary compensated signal is fed to a second interpolator 650 and a second delay 680.
  • the second interpolator 650 is preferably a sync or Nyquist interpolator and estimates fading relating to the primarily compensated data as shown in FIG. 7.
  • the second interpolator 650 estimates fading relating to the primarily compensated symbols (marked with slash lines) preceding and following a data symbol S to be estimated. Pilot symbols P1, P2, P3, and P4 that were used for the primary compensation may be used along with the primarily compensated symbols for the secondary channel estimation. The same weight or different weights can be given to the primarily compensated data symbols and the pilot symbols.
  • a level controller 660 controls the level of the estimated value. For example, if reference symbols are (1, 0) and (-1, 0), all symbols are shifted to a (1, 0) domain by generalizing the other quadrature phase-shift keying (QPSK) symbols (0, 1) and (0, -1), for achieving the channel estimated value.
  • QPSK quadrature phase-shift keying
  • a second inverter 670 inverts the level-controlled signal and a multiplier 690 secondarily compensates the delayed signal received from the second delay 680 by multiplying the delayed signal by the inverted signal received from the second inverter 670.
  • the channel of the symbol S is estimated through the primary estimation using pilot symbols and the secondary estimation using symbols compensated for by the Wiener interpolator 610 as new pilot symbols using the Nyquist interpolator 650.
  • the Nyquist interpolator 650 is used for the secondary channel estimation because the primarily compensated symbols related thereto are located near the symbol to be estimated.
  • data symbols are more accurately channel-estimated as signal to noise ratio (SNR) increases and use of compensated data symbols along with the pilot symbols increases channel estimation reliability.
  • SNR signal to noise ratio
  • FIGs. 8A to 8D illustrate BER characteristics according to the embodiment of the present invention.
  • the horizontal axis of each of FIGs. 8A to 8D represents Es/No and the vertical axis represents BER variations.
  • Table 1 lists experimental data. TABLE 1 Figure K fd 8A 7dB 20Hz 8B 7dB 200Hz 8C 12dB 20Hz 8D 12dB 200Hz
  • performance is improved in the embodiment of the present invention, as compared to performance in a conventional Wiener interpolator using scheme.
  • K denotes a Ricean fading factor and fd is a Doppler frequency.
  • Normalized Doppler frequencies (fdT) are 0.0011 and 0.011, that is, 20Hz and 200Hz in the case where a symbol rate is 18,000 symbols per second.
  • a pilot insertion period M is 20.
  • a channel is primarily estimated using pilot symbols and secondarily estimated using the primarily compensated symbols. Therefore, channel estimation can be performed even at severe distortion caused by fading.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Power Engineering (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)

Claims (6)

  1. Appareil d'estimation de canal dans un système de communication radio, comprenant :
    un estimateur d'évanouissement (600), destiné à estimer un canal en utilisant des symboles prédéterminés d'un signal d'entrée ;
    un premier interpolateur (610), destiné à interpoler d'autres symboles du signal d'entrée, sur la base de l'estimation de l'évanouissement ;
    un premier multiplicateur (640), destiné à appliquer une première compensation à un signal de sortie d'un premier circuit à retard, à l'aide d'un signal de sortie d'un premier inverseur ;
    caractérisé par
    le premier inverseur (620), destiné à inverser un signal de sortie du premier interpolateur ;
    le premier circuit à retard (630), destiné à retarder le signal d'entrée d'une période de temps prédéterminée ;
    un second interpolateur (650), destiné à interpoler chaque symbole du signal d'entrée qui est lié aux symboles ayant subi la première compensation, sur une période prédéterminée avant et après le symbole ;
    un contrôleur de niveau (660), destiné à commander le niveau d'un signal de sortie du second interpolateur ;
    un second inverseur (670), destiné à inverser un signal de sortie du contrôleur de niveau ;
    un second circuit à retard (670), destiné à retarder un signal ayant subi une première compensation d'une période de temps prédéterminée ; et
    un second multiplicateur (690), destiné à appliquer une seconde compensation à un signal de sortie du second circuit à retard, à l'aide d'un signal de sortie du second inverseur.
  2. Appareil d'estimation de canal selon la revendication 1, dans lequel le premier interpolateur est un interpolateur de Wiener.
  3. Appareil d'estimation de canal selon la revendication 1 ou 2, dans lequel le second interpolateur est soit un interpolateur de synchronisation, soit un interpolateur de Nyquist.
  4. Appareil d'estimation de canal selon l'une des revendications 1 à 3, dans lequel les symboles prédéterminés sont des symboles pilotes.
  5. Procédé d'estimation de canal, dans un système de communication radio, comprenant les étapes consistant à :
    estimer un canal en utilisant des symboles prédéterminés ; et
    interpoler, à l'aide d'un premier interpolateur (610), d'autres symboles d'un signal d'entrée, sur la base d'une estimation du canal, et obtenir un premier signal interpolé ; et
    appliquer une première compensation au signal d'entrée, à l'aide d'un premier signal inversé, et obtenir un signal ayant subi la première compensation ;
    caractérisé par les étapes consistant à :
    inverser, à l'aide d'un premier inverseur (620), le premier signal interpolé et obtenir le premier signal inversé ; et
    interpoler, à l'aide d'un second interpolateur (650), chaque symbole lié à des symboles ayant subi la première compensation et obtenir des seconds symboles interpolés ; et
    commander, à l'aide d'un contrôleur de niveau (660), le niveau des seconds symboles interpolés et obtenir un signal à niveau commandé ; et
    inverser, à l'aide d'un second inverseur (670), le signal à niveau commandé ; et
    appliquer une seconde compensation au signal compensé ayant subi la première compensation.
  6. Procédé d'estimation de canal selon la revendication 5, dans lequel les symboles prédéterminés sont des symboles pilotes.
EP00128658A 1999-12-29 2000-12-28 Dispositif et procédé d'estimation de canal dans un système de communication par radio Expired - Lifetime EP1113633B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
KR1019990065273A KR100318952B1 (ko) 1999-12-29 1999-12-29 무선통신시스템에서 채널 추정을 위한 장치 및 방법
KR6527399 1999-12-29

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EP1113633A2 EP1113633A2 (fr) 2001-07-04
EP1113633A3 EP1113633A3 (fr) 2004-01-02
EP1113633B1 true EP1113633B1 (fr) 2006-11-29

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US (1) US6751274B2 (fr)
EP (1) EP1113633B1 (fr)
JP (1) JP3652247B2 (fr)
KR (1) KR100318952B1 (fr)
CN (1) CN1166080C (fr)
DE (1) DE60032109T2 (fr)

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Publication number Publication date
CN1166080C (zh) 2004-09-08
CN1308417A (zh) 2001-08-15
US20010006540A1 (en) 2001-07-05
KR100318952B1 (ko) 2002-01-04
JP3652247B2 (ja) 2005-05-25
JP2001217882A (ja) 2001-08-10
EP1113633A2 (fr) 2001-07-04
KR20010065396A (ko) 2001-07-11
US6751274B2 (en) 2004-06-15
DE60032109D1 (de) 2007-01-11
DE60032109T2 (de) 2007-03-08
EP1113633A3 (fr) 2004-01-02

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